Use of membrane filters for measurement of mycobactericidal activity of alkaline glutaraldehyde solution

Abstract

Bactericidal assays of 2% alkaline glutaraldehyde solution were carried out using Millipore membranes, and the rate of kill was compared with that of mycobacteria in suspension and on Penicylinder surfaces when using the methods recommended for the official tuberculocidal test. The rate of ina,ctivation observed on the membrane filter surface was similar to that achieved using Penicylinders. The absence of visible colonies on the treated membranes provided a direct demonstration of sterility. The use of filter membranes in tuberculocidal tests provides a simple quantitative assay.

Effect of methodology, dilution, and exposure time on the tuberculocidal activity of glutaraldehyde-based disinfectants

“…All required activation prior to use. The type of product, use life after activation, recommended use-dilution, and tuberculocidal label claim (for 100% kill) were 2% alkaline glutaraldehyde, 14 days, undiluted, and 45 min at 25°C, respectively, for disinfectant A; 2% alkaline glutaraldehyde, 14 days, undiluted, and 20 min at 20°C, respectively, for disinfectant B; and 2% alkaline glutaraldehyde-7.05% phenol-1.2% sodium phenate, 30 days, diluted 1:16, and 10 min at 20°C, respectively, for disinfectant C. All products were used within their specified use life. Dilutions of disinfectant C were freshly prepared each day.…”

Activity of biocides against mycobacteria

“…A membrane filtration method, in which washing in situ removes residual biocide and in which colony counting is facilitated on the membrane itself, has been described by Ascenzi et al (1986) and by Collins (1987). Carrier methods are considered by Leers et al (1974), Davis et al (1984, Collins (1986a), Best et al (1988 and Mbithi et al (1993).…”

Comparative mycobactericidal efficacy of chemical disinfectants in suspension and carrier tests

“…The Association of Official Analytical Chemists tuberculocidal test (3), currently widely used, has been recently criticized (1, 6-8) and is now generally recognized to be inadequate and unreliable. Several new quantitative tuberculocidal suspension tests have been proposed (2,10,16). These tests are useful for screening disinfectants; however, to evaluate disinfectants used on contaminated surfaces, it is necessary to use a carrier test which simulates the in-use practices of general surface and equipment disinfection.…”